Dear Tom and Ray:

My dad, who knew more about cars and engines that anyone I ever knew, swore by the benefits of Marvel Mystery Oil. He always poured MMO in the crankcase at each oil change and sometimes put it in the gas tank. His cars always made it to 200,000 miles. Will Marvel Mystery Oil harm a modern engine? My 1997 Ford Ranger has developed an occasional noisy lifter problem that the dealer can't replicate. Harking back to my dad's experience, I'm tempted to dump a can of MMO in the tank and crankcase, but one of the dealer's mechanics said he wouldn't do it because the factory recommends against additives. There's nothing in the manual about additives. What do you think? -- Les

Ray: Marvel Mystery Oil is kind of like chicken soup, Les. It probably won't help, but it can't hurt.

Tom: The reason most manufacturers make a blanket recommendation against additives is because there are too many to keep track of. There are thousands of additives on the market these days. Several of them probably even contain chicken soup.

Ray: Most of them, like MMO, probably won't hurt your car, but it's impossible for the manufacturers to test them all. So they play it safe and don't recommend any of them.

Tom: And I doubt the MMO will solve your lifter problem, which could be caused by low oil pressure. So have your oil pressure tested. The lifter could also be leaking down, which is common these days with self-adjusting lifters. A lot of them are just not "beefy" enough by design, in my opinion.

Ray: But feel free to try MMO. And if that doesn't work, try some Haley's M-O. My brother puts that in his '63 Dodge Dart. It doesn't do anything for his lifters either, but the car is incredibly regular.

© 1999 by Tom and Ray Magliozzi and Doug Berman Distributed by King Features Syndicate, Inc.

Don't get stuck with a lemon. Be an informed shopper. Read Tom and Ray's guide "How to Buy a Great Used Car: Secrets Only Your Mechanic Knows." To order, send (check or money order) to Ruin, P.O. Box 536475, Orlando, FL 32853-6475. You can also order online.

© 1999 by Tom and Ray Magliozzi and Doug Berman Distributed by King Features Syndicate, Inc.

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